src/styles/components/select-dropdown.less

@select-dropdown-prefix-cls: ~"@{css-prefix}select-dropdown";
.@{select-dropdown-prefix-cls} {
    width: inherit;
    max-height: 200px;
    overflow: auto;
    margin: 5px 0;
    padding: 5px 0;
    background-color: #fff;
    box-sizing: border-box;
    border: 1px solid @border-color-split;
    border-radius: @btn-border-radius;
    //box-shadow: 0 1px 3px rgba(0,0,0,.2);
    box-shadow: @shadow-base;
    position: absolute;
    z-index: @zindex-select;
}